class Solution
{
    int m, n;
    int dx[4] = { -1 , 1, 0, 0 }, dy[4] = { 0, 0, 1, -1 };
    bool vis[501][501];
public:
    int numEnclaves(vector<vector<int>>& grid)
    {
        m = grid.size(), n = grid[0].size();

        queue<pair<int, int>> q;
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (i == 0 || i == m - 1 || j == 0 || j == n - 1)
                    if (grid[i][j] == 1)
                    {
                        q.push({ i, j });
                        vis[i][j] = true;
                    }

        while (q.size())
        {
            auto [a, b] = q.front();
            q.pop();
            for (int i = 0; i < 4; i++)
            {
                int x = a + dx[i], y = b + dy[i];
                if (x >= 0 && y >= 0 && x < m && y < n && !vis[x][y] && grid[x][y] == 1)
                {
                    q.push({ x, y });
                    vis[x][y] = true;
                }
            }
        }

        int ret = 0;
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (!vis[i][j] && grid[i][j] == 1)
                    ret++;

        return ret;
    }
};